Vacuum waste systems are generally known in the art for use in transportation vehicles such as aircraft. Vacuum waste systems typically comprise a toilet bowl connected by vacuum piping to a waste tank. A flush valve is disposed between the toilet and the vacuum piping. When the flush valve opens, the contents of the toilet bowl are removed by differential pressure to the waste tank because the air pressure in the line under vacuum is lower than ambient air pressure in a toilet bowl. The flush valve maintains the pressure boundary between ambient air in the toilet bowl and the lower pressure of the piping and the waste tank. In an aircraft, the piping may be placed under vacuum pressure at altitudes under about 16,000 feet by a vacuum source. At altitudes about 16,000 feet and above, the vacuum pressure in the piping may be supplied by the atmospheric pressure differential between the cabin and the exterior of the airplane.
Conventional flush valves and methods for controlling the removal of waste from the toilet bowl to a waste tank are generally known. Such prior flush valves may use a large, rotating disk having an aperture to admit waste past the aperture. The use of such a large disk is undesirable because it makes the overall flush valve large, heavy and unwieldy for use in confined places such as aircraft lavatories.
Furthermore, the use of a disk having an aperture requires precise positioning of the aperture over the waste inlet so that waste moving from the toilet bowl to the piping leading to the waste tank does not catch or accumulate on the perimeter of the aperture or on the solid portion of the disk causing the disk to stick or not seal properly. Also, over time and due to normal wear, the accuracy of the positioning of such disk apertures tend to slip, aggravating the aforementioned problems.
Another problem with conventional flush valves using a disk with an aperture to admit waste past the disk is that users are not able to open them manually. This can result in unsanitary back-up of waste in the toilet bowl and overflow of waste from the toilet bowl into the lavatory area if the flush valve becomes stuck in the closed position.
A need exists for a smaller, easily installed and more efficient flush valve, which does not rely on a disk having an aperture, for controlling the removal of waste from toilet bowls in a vacuum toilet systems.